The viewability of the display screen of a color cathode ray tube can be improved by flattening the outer panel surface thereof. However, in a shadow mask type color cathode ray tube, it is necessary that the effective surface section of its shadow mask be given a curvature in order to maintain the mechanical strength of the shadow mask. To this end, even if the outer panel surface is made flat, it is necessary to give a curvature to the inner surface of a panel that opposes the shadow mask. This art is disclosed in Japanese Patent Laid-Open No. 64451/1998.
There are also demands for reductions in the entire lengths of color cathode ray tubes so that the spaces of display monitor sets can be made compact. A general method of reducing the entire length of such a color cathode ray tube is to increase the deflection angle of an electron beam. In a related-art cathode ray tube whose outer panel surface is round (a curved shape), deflection angles of 90xc2x0, 100xc2x0 and 110xc2x0 are employed. An increase in the deflection angle offers the merits of reducing the entire length of the cathode ray tube and reducing the distance between its main lens and its phosphor screen, thereby improving focus. However, in a cathode ray tube whose outer panel surface is flat, if the deflection angle is made large, there occurs the problem that raster distortion increases or a neck shadow easily occurs. Accordingly, there has not yet been any related art that can realize a cathode ray tube whose outer panel surface is flat and which has the required display performance.
The color cathode ray tube (color display tube) according to the present invention has a panel whose outer surface is nearly flat, and the entire length of the cathode ray tube can be reduced with the distortion of its screen raster being suppressed within a practical range, in spite of its sufficient neck shadow tolerance.
In the color cathode ray tube according to the present invention, letting D, Tc and Td be, respectively, half of a diagonal effective diameter, the glass thickness of the panel at the center thereof, and the glass thickness of a diagonal end of the effective screen, (Tdxe2x88x92Tc)/D is set to 7.5% or less and the maximum deflection angle of an electron beam is set be between 96xc2x0 and 99xc2x0.